Lines Matching refs:CPU
4 Using RCU's CPU Stall Detector
7 This document first discusses what sorts of issues RCU's CPU stall
13 What Causes RCU CPU Stall Warnings?
16 So your kernel printed an RCU CPU stall warning. The next question is
17 "What caused it?" The following problems can result in RCU CPU stall
20 - A CPU looping in an RCU read-side critical section.
22 - A CPU looping with interrupts disabled.
24 - A CPU looping with preemption disabled.
26 - A CPU looping with bottom halves disabled.
28 - For !CONFIG_PREEMPT kernels, a CPU looping anywhere in the kernel
37 RCU CPU stall warning messages. Especially if you have added
47 - A CPU-bound real-time task in a CONFIG_PREEMPT kernel, which might
50 that low-priority task is not permitted to run on any other CPU,
56 - A CPU-bound real-time task in a CONFIG_PREEMPT_RT kernel that
77 RCU CPU stall warnings.
80 timeout down to just barely avoid RCU CPU stall warnings, and then
86 interrupt on a CPU that is not in dyntick-idle mode. This
88 result in RCU CPU stall warnings for CONFIG_NO_HZ_COMMON=n kernels.
100 at least once in real life. A CPU failed in a running system,
102 This resulted in a series of RCU CPU stall warnings, eventually
103 leading the realization that the CPU had failed.
105 The RCU, RCU-sched, and RCU-tasks implementations have CPU stall warning.
106 Note that SRCU does -not- have CPU stall warnings. Please note that
107 RCU only detects CPU stalls when there is a grace period in progress.
108 No grace period, no CPU stall warnings.
123 Fine-Tuning the RCU CPU Stall Detector
127 CPU stall detector, which detects conditions that unduly delay RCU grace
128 periods. This module parameter enables CPU stall detection by default,
138 issues an RCU CPU stall warning. This time period is normally
159 giving an RCU CPU stall warning message. (This is a cpp
165 The CPU stall detector tries to make the offending CPU print its
167 However, if the offending CPU does not detect its own stall in
169 some other CPU will complain. This delay is normally set to
187 Interpreting RCU's CPU Stall-Detector "Splats"
190 For non-RCU-tasks flavors of RCU, when a CPU detects that it is stalling,
198 This message indicates that CPU 32 detected that CPUs 2 and 16 were both
200 will normally be followed by stack dumps for each CPU. Please note that
206 CPU 2's "(3 GPs behind)" indicates that this CPU has not interacted with
207 the RCU core for the past three grace periods. In contrast, CPU 16's "(0
208 ticks this GP)" indicates that this CPU has not taken any scheduling-clock
213 dynticks counter, which will have an even-numbered value if the CPU
220 handlers that the stalled CPU has executed. The number before the "/"
221 is the number that had executed since boot at the time that this CPU
224 example, if the CPU might have been in dyntick-idle mode for an extended
228 handlers are no longer able to execute on this CPU. This can happen if
229 the stalled CPU is spinning with interrupts are disabled, or, in -rt
234 CPU since the last time that this CPU noted the beginning of a grace
237 The "detected by" line indicates which CPU detected the stall (in this
238 case, CPU 32), how many jiffies have elapsed since the start of the grace
244 for each CPU::
249 jiffies counter when this CPU last invoked rcu_try_advance_all_cbs()
286 Starving the grace-period kthreads of CPU time can of course result
287 in RCU CPU stall warnings even when all CPUs and tasks have passed
293 kthread last ran on CPU 5.
314 This indicates that CPU 7 has failed to respond to a reschedule IPI.
315 The three periods (".") following the CPU number indicate that the CPU
317 that the CPU was online at the beginning of the expedited grace period
319 the CPU has been online at least once since boot (otherwise, the third